When conveyor belts are required to operate in non-environmentally controlled conditions where they are subjected to abrasives, their life span is considerably shortened by frictional contact between relatively movable parts in the presence of the abrasives. Even in the absence of grit and other abrasives, belt wear in the vicinity of relatively movable parts is the most significant factor in terminating the useful life span of the belt.
In modular link conveyor belts, modular links are traditionally interdigitated at opposite ends and linked together by means of pivot pins extending through the interlaced belt end fingers in a pattern forming a conveyor surface. The links need to have articulated joints for passing over sprockets, for example, conventionally provided by means of the pivot pins.
These pivot pins have provided many problems in construction and operation. If they are rigidly mated in tight fitting mating apertures, there is little room for thermal expansion for example which can change dimensions enough to introduce greater wear, binding or inability to flex when under load or impact conditions. If the pivot pins are slidable or loosely fitted, they induce significant frictional wear particularly in abrasive environments where grit can accumulate in the vicinity of the pivot pin bearings. Because of forces acting upon the pivot pins they may be forced axially out of position with loading or torsion conditions in the belt. This requires countermeasures such as riveted heads on the pivot pins, snap catches, and the like. With conventional cylindrical pivot pins, the articulation wear when the belt goes around sprockets, etc., generally leads to belt failure. If the pins are replaceable, repairs may be made, but they are not always easily accessible for removal, since they must be retained in place securely during normal belt operation by heads or retaining structure so that they will not be moved out of position. The expense of pin construction with retention heads and corresponding link means specially provided to hold the pivot pins in place is objectionable as well as the assembly costs because there are many links connected together in a belt.
A major problem encountered is the accumulation of dirt and grit in the vicinity of the pivot pin wear surfaces, casing accelerated abrasive wear and early belt failure.
This frictional pivot pin wear has to some extent been eliminated by the provision of a flexible strip forming a so-called "living hinge" replacing the conventional pivot pin in J. M. Lapeyre U.S. Pat. No. 4,140,025; Feb. 20, 1979 entitled Link Chain Having Non-frictional Couplings. Therein, the flexible strips replacing pivot pins are secured to the interdigited links so that the flexible web forms articulation means at a hinging joint that does not frictionally slide over link surfaces or require journalling in a bearing surface.
This prior art belt worked well under light load conditions and for some applications. However, for universal adaptability to a range of operation conditions, that belt system presented a different set of unsolved problems. For example, the material being hinged could be buckled under high belt tension loads. The hinging effect also eventually causes catastrophic life ending fatigue in the fabric material requiring complicated maintenance procedures. Failure is particularly induced under heavy belt loads causing tension in the fabric as the joined links pull apart from each other, leaving the fabric to bear the belt tension load. This reduced the belt load bearing capacity. Furthermore, the accompanying belt array presented other operational limitations, such as the inability to produce a flat substantially unapertured belt conveyance surface, a belt surface that resists torsion caused by load objects, and smooth continuous belt edges that can ride upon an adjoining guide rail.
Accordingly, it is an objective of this invention to provide improved conveyor belts and accompanying articulation means resolving the foregoing disadvantages of both conventional pivot pin connected link belts and those employing substantially frictionless living hinge articulation means.